Rule 201.4b

If an ability of an object refers to that object by name, and an object with a different name gains that ability, all instances of the first name in the gained ability should be treated as the second name. Example: Quicksilver Elemental says, in part, “{U}: Quicksilver Elemental gains all activated abilities of target creature until end of turn.” If it gains an ability that says “{B}: Regenerate Drudge Skeletons,” activating that ability will regenerate Quicksilver Elemental, not the Drudge Skeletons it gained the ability from. Example: Glacial Ray is an instant with “splice onto Arcane” that says “Glacial Ray deals 2 damage to target creature or player.” If it’s spliced onto a Kodama’s Reach, that Kodama’s Reach deals 2 damage to the target creature or player. Example: Dimir Doppelganger says “{1}{U}{B}: Exile target creature card from a graveyard. Dimir Doppelganger becomes a copy of that card and gains this ability.” Dimir Doppelganger’s ability is activated targeting a Runeclaw Bear card. The Doppelganger becomes a copy of Runeclaw Bear and gains an ability that should be treated as saying “{1}{U}{B}: Exile target creature card from a graveyard. Runeclaw Bear becomes a copy of that card and gains this ability.”

Find this number in the current Rules